The Raiders spent the first day of NFL free agency trying to add another key piece to what has already been a solid haul.

The team is focused on landing Kansas City cornerback Sean Smith, who according to multiple reports is deciding among the Raiders, 49ers and a late push by the Chiefs to retain the eight-year veteran.

The secondary is the team’s primary area of need, and Smith is Oakland’s top target available to bolster a defense already expected to add former Seattle Seahawks linebacker Bruce Irvin.

Irvin, along with former Baltimore Ravens offensive lineman Kelechi Osemele, agreed to terms with the team on Tuesday during the league’s negotiating period, but the Raiders did not officially announce the deals Wednesday.

Both players, however, took to social media to announce their intentions to come with Oakland.

Irvin, who spent the first four years of his career with the Seahawks before agreeing to a reported four-year, $37 million deal in Oakland, penned a farewell to Seattle via Instagram.

In that post, Irvin wrote, “I’m looking forward to my new chapter and helping the city of Oakland bring a ship there.”

Irvin also wrote to the fans in Seattle, saying: “I know some may not understand the decision but this window of opportunity is so small that you have to make the best decision for you and your family.”

Osemele, who has reportedly agreed to a five-year, $60 million deal with $24.5 million guaranteed, tweeted out an icon of a skull commonly used to reference the Raiders along with, “Perfect Fit.” Both players also received welcome tweets from quarterback Derek Carr.

The Raiders did see one of their 11 unrestricted free agents depart Wednesday, with the Houston Chronicle reporting that offensive lineman Tony Bergstrom agreed to a deal with the Houston Texans.

Bergstrom was general manager Reggie McKenzie’s first draft pick with the Raiders when he was selected in the third round in 2012 (Oakland didn’t have first- or second-round picks that season). He played in 25 games with four starts during his four years in Oakland.

A tackle in college, he came to the Raiders as a guard, and his lone start his rookie year came at right guard. He missed his entire second year in the NFL with a training camp foot injury that landed him on injured reserve and then was a healthy inactive for all 16 games in 2014.

Bergstrom added versatility to his game as the team’s backup center this past season and made three starts when Rodney Hudson battled an ankle injury.